<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>必应搜索框</title>
    <style>
      body {
        background-color: #333;
        margin: 0;
        padding: 0;
      }
      .bg-div {
        box-sizing: border-box;
        background-image: url(img/river.jpg);
        background-repeat: no-repeat;
        background-size: cover;
        width: 100vw;
        height: 100vh;
        margin: 0 auto;
      }
    </style>
  </head>
  <body>
    <div class="bg-div"></div>
  </body>
</html>